Gas operated firearms are well known. Gas operated firearms use some of the gas from a cartridge being fired to extract the spent case of the cartridge and to chamber a new cartridge. The gas travels from a port in the barrel to a gas cylinder where the gas pushes a piston within the gas cylinder to operate a mechanism for extracting the spent case and for chambering the new cartridge. In some firearms, such as the M16 and the M4, the gas cylinder is formed in the bolt carrier and the piston is part of the bolt. In such firearms, gas is provided from the barrel to the gas cylinder by a gas tube.
In other firearms, such as the HK416, a separate (not part of the bolt) piston is used. The piston is disposed in a gas cylinder that is not part of the bolt carrier. This separate piston applies force through a tappet or operating rod and a bolt carrier to operate the mechanism for extracting the spent case and for chambering the new cartridge.
Whether or not the piston is part of the bolt, it is desirable to prevent gas leakage between the piston and the cylinder. Contemporary gas operated firearms commonly use a plurality of piston rings which fit into a groove of the piston and provide a gas seal between the piston and the cylinder to mitigate gas leakage. For example, the M16, M4, and HK416 use three rings. Each of the rings is a split ring that has a gap formed therein to facilitate installation of the ring and to apply an outward spring force that tends to seal the loose fit between the piston and the cylinder.
Contemporary rings possess inherent deficiencies which detract from their overall effectiveness and desirability. For example, the gaps of the three rings occasionally line up in a manner that allows hot gasses to flow readily through the gaps and thereby undesirably bypass the rings. Contemporary gas tubes also possess inherent deficiencies which detract from their effectiveness and desirability. For example, contemporary gas tubes can overheat and lose strength, particularly during sustained fully automatic fire of the firearm.
The higher level of heat associated with sustained fully automatic fire can result in undesirable thermal expansion of the gas tube both radially and longitudinally. Such thermal expansion can be substantially beyond an amount accommodated by the available space in the firearm. Such thermal expansion can result in sliding/clearance fits becoming interference fits. That is, a sliding fit can undesirably become a non-sliding fit. When the gas tube heats up excessively, the weakened and expanded gas tube can bend and be damaged, thus causing the firearm to become inoperative. As such, it is desirable to provide methods and systems for mitigating overheating in gas operated firearms.
Forward and rearward bouncing of the bolt carrier can cause the cyclic rate of a firearm to increase substantially. This increase in the cyclic rate can reduce the reliability of the firearm and can increase wear on the firearm, as discussed herein. As such, it is desirable to provide methods and systems for mitigating both forward and rearward bouncing of the bolt carrier.
The gas port of a contemporary M16/M4 firearm is subject to erosion caused by bullet scrubbing and propellant bombardment. Such erosion results in enlargement of the gas port and consequently an undesirable increase in the cyclic rate of the firearm over time. This undesirable increase in the cyclic rate can eventually result in malfunction and damage to the firearm. As such, it is desirable to provide for the metering of gas in a manner that does not result in an increased cyclic rate over time.